6082–T6/7075–T6异种铝合金搅拌摩擦焊接接头应力腐蚀行为

Stress Corrosion Behavior of 6082-T6/7075-T6 Dissimilar Aluminum Alloy Friction Stir Welded Joints

为提高航空、航天运载工具异种高强度铝合金零部件搅拌摩擦焊接接头在腐蚀环境下的服役可靠性,采用金相分析、电子显微分析和四点弯曲应力腐蚀法,对经过T6处理的6 mm厚6082–T6/7075–T6异种铝合金搅拌摩擦焊接接头应力腐蚀行为进行了研究。结果表明,搅拌头转速1200 r/min、焊接速度80 mm/min条件下,6082–T6/7075–T6母材获得了具有“洋葱环”结构的致密、成形良好的搅拌摩擦焊接接头组织。6082–T6和7075–T6母材搅拌摩擦焊接接头四点弯曲应力腐蚀主要发生在后退侧的7075–T6铝合金一侧,而前进侧6082–T6铝合金一侧表现出较好的耐蚀性。这主要是由于异种铝合金母材电极电位差异导致焊接接头发生应力作用下的电偶腐蚀所致。此外,α–Al基体与第二相形成微区电偶对,以及焊接接头热机械影响区(TMAZ)、热影响区(HAZ)和母材区(BM)存在的大角度晶界也是造成应力腐蚀的重要原因。

In order to improve the service reliability of friction stir welded joints of high-strength aluminum alloy components for aviation and aerospace vehicles in corrosive environments,the stress corrosion behavior of 6 mm thick 6082–T6/7075–T6 dissimilar aluminum alloy friction stir welded joints treated with T6 was studied using metallographic analysis,electron microscopy analysis,and four-point bending stress corrosion method.The results showed that under the conditions of rotating speed 1200 r/min and weeding speed 80 mm/min,the 6082–T6/7075–T6 base material obtained a dense and well formed friction stir welded joint structure with an onion ring structure.The four-point bending stress corrosion of 6082–T6 and 7075–T6 base metal friction stir welded joints mainly occurs on the 7075–T6 aluminum alloy side on the retreating side,while the 6082–T6 aluminum alloy side on the advancing side shows good corrosion resistance.This is mainly due to the difference in electrode potential between dissimilar aluminum alloy base materials,which leads to galvanic corrosion of welded joints under stress.In addition,The formation of micro electric couples between theα–Al matrix and the second phase,as well as the presence of large angle grain boundaries in the TMAZ,HAZ,and BM regions of the welded joint,are also important reasons for stress corrosion.